propagate_one(): mnt_set_mountpoint() needs mount_lock (b0d3869c) · Commits · 戴 / test

... to protect the modification of mp->m_count done by it. Most of the places that modify that thing also have namespace_lock held, but not all of them can do so, so we really need mount_lock here. Kudos to Piotr Krysiuk <piotras@gmail.com>, who'd spotted a related bug in pivot_root(2) (fixed unnoticed in 5.3); search for other similar turds has caught out this one. Cc: stable@kernel.org Signed-off-by:

Al Viro <viro@zeniv.linux.org.uk>

fs/pnode.c

+4 −5

Original line number	Diff line number	Diff line
		@@ -261,14 +261,13 @@ static int propagate_one(struct mount *m)
		child = copy_tree(last_source, last_source->mnt.mnt_root, type);
		if (IS_ERR(child))
		return PTR_ERR(child);
		mnt_set_mountpoint(m, mp, child);
		last_dest = m;
		last_source = child;
		if (m->mnt_master != dest_master) {
		read_seqlock_excl(&mount_lock);
		mnt_set_mountpoint(m, mp, child);
		if (m->mnt_master != dest_master)
		SET_MNT_MARK(m->mnt_master);
		read_sequnlock_excl(&mount_lock);
		}
		last_dest = m;
		last_source = child;
		hlist_add_head(&child->mnt_hash, list);
		return count_mounts(m->mnt_ns, child);
		}

Admin message